Microwave oscillator device



March 24, 1959 1 w. ROBERTS 2,879,438 7 MICROWAVE} OSCILLATOR DEVICE Filed Dec. 25, 1957 2 Sheets-Sheet 1 INVENTOR. LOLHS w. zoasers RG1 BY AT T'OZN av March 24, 1959 L. w. ROBERTS 2,879,438

MICROWAVE OSCILLATOR DENISE Filed Dcl 23; 1957 2 Sheets-Sheet 2 INVENTOR.

" v 5b LOLHS w. nzosszrs ATTORNEY United States Patent "ice,

2,879,438- MICROWAVE OSCILLATOR ,DEVlCE' Louis W. Roberts, Boston, 'Mass., assignor to Bomac Laboratories. Inc., Beverly, Mass, a. corporation. of?

Massachusetts Application December 23, 1957, Serial No. 704,705

2'Claims. (Cl. SIS-3.5)

The present invention"relates generally to electron discharge devices and more particularly to. backward wave oscillator and/or amplifier tubes having crossed electric and magnetic field's.

The embodiment of the invention commonly comprises spaced parallel circular conductors defining therebetween an interaction space. An electron beam formed by a suitable gun structure traverses the interaction space and is influenced by the crossed electric and magnetic fields established therein. One of the conductors is a delay line having interdigital metallic fingers which provides means for the propagation of the backward traveling wave. Suitable coaxial output conduction means are coupled to the delay line.

Generally biasing voltage differentials provided by the parallel conductors as well as a grid and accelerator electrode control the electron beam configuration. Mechanical variations, however, may result in the tube assembly which will materially alter the electron beam configuration. A control element may, therefore, be provided to compensate for such mechanical variations and is referred to as the dummy anode. Desira-bly the element is positioned adjacent to the first member of the delay line and accurate adjustment will assure successful operation of the tube.

An object of the present invention, therefore, is the provision of an improved control element for microwave oscillator and/ or amplifier devices.

A further object is the provision of an improved control element for microwave oscillator and/ or amplifier devices that is readily adjustable after assembly of the complete device.

Briefly, the invention attains the objects enumerated by the provision of a dummy anode member, supported by an adjusting mechanism which provides for external activation to move the member in a direction approximately normal to the electron beam. The vacuum condition of the device is maintained by means of a flexible diaphragm secured between the anode member and adjusting mechanism. With the improved control element of the invention, performance may be optimized desirably during electrical testing on the complete tube. In most instances improved efficiency has been measurably noted over prior art tubes wherein the dummy anode member position is fixed.

The invention will now be described in detail, reference being directed to the accompanying drawings, in which:

Fig. 1 is a perspective view of an illustrative embodiment with the present invention shown in a cut-away crosssection;

Fig. 2 is an enlarged cross-sectional view of the gun structure and the present invention to illustrate the relationships of the electrode structure of embodiment; and

Fig. 3 is a view along the line 3-3 in Fig. 2.

Referring to the drawings Fig. 1 illustrates the embodiment of the invention, the magnets having been omitted to reveal the tube construction. The circular metallic body member 1 is enclosed by top and bottom cover plates 2,879,438 PietentedMar. 24, 1959 suitable inlet and outlet ports for circulating a coolant.

such as water or oil.. Positioned within the envelope are circular paralleljmetallic conductorscomprising a substantially solid inner circular electrod'e'4 referred to as the sole and an outer multifingered.interdigital delay linev 5' comprising opposed fingers 5A and 58 shown in Fig. 3. With the delay line and body member at ground potential andthe sole electrode at ahigher negative potential with respect to the cathode an electric field is established in the interaction space 6'. Collector. 7 is positioned at the end of delay line 5 to trap the electrons which havenot entered the delay line from the electron beam.

The electron gun structure is housed within the sole electrode 4 and comprises an. elongated cathode S heated by an internal heater 9 having a suitable external conductor 10. A grid electrode 11' surrounds the cathode as shown and controls the emission by having substantially the same potential as the cathode or a potential slightly more negative with respect to the cathode. An accelerator anode 12 of a thin strip of metallic material is positioned as shown and has a potential between 900 1000 volts higher than the cathode to thereby produce acceleration of electrons emitted from cathode 8. The complete gun assembly is supported between end shields 13, one of which is shown. Connector leads 16 extend through the sole input section 14 secured to cover plate 2 with cooling fins 15 provided thereon. Leads 16 are connected to the accelerating anode, grid and cathode with appropriate markings or color coding to identify the appropriate electrodes. The sole electrode is directly connected by means of input section 14.

The radio frequency power induced in the delay line may be coupled to the external waveguide system by means of a coaxial output line 17 having its center conductor 18 secured to the first finger 19 of delay line 5. The oscillator type device is provided with a single output while an amplifier would have input and output connections.

The electron trajectory after leaving the cathode surface assumes an epicycloidal path as illustrated by the curve 20 before entering the interaction space 6. The dummy anode 21 is, therefore, positioned in the critical region near the start of the delay line to thereby influence the electron beam configuration. It will be noted that surface 22 of the dummy anode is substantially parallel to the sole electrode 4, while inclined surface 23 is angularly disposed with respect to the axis of output conductor 17. Hence surface 23 acts as a microwave deflector for the radio frequency wave in the delay line, as well as an element affecting the electron beam configuration. The overall length of the anode 21 member is substantially equivalent to the length of the fingers of the delay line.

While it is possible to secure the dummy anode member directly to the body member 1, l have observed that compensation for mechanical variations in the gun structure or other components necessary in the electron optical system is vastly improved by providing for adjustment of the anode member after initial positioning. The adjusting mechanism is introduced into the body member by means of a passageway 24 with the base 25 secured therein as by brazing. Dummy anode member 21 is aflixed to a support bar 26 which in turn is attached to a cylindrical plate 27 of the movable piston assembly by means of a screw 28. The piston assembly comprises a shaft 29, hub portion 30 and disc member 31 with the plate 27 secured within the hub portion 30 as at 32. A deformable diaphragm 33 brazed or soldered to the hub 30 and base 25 provides for maintaining the vacuum condition of the device.

A differential screw assembly 34 comprises a main barrel portion 35 engaging a shoulder 36 of base 25. Barrel 35 has a partition '37 with a "threaded aperture therein to receive screw 38: having an outer thread and an internal threaded passageway 39 to engage the shaft 29 which is also threaded. A slot 40 in screw 38 provides for insertion of a hand tool for rotation thereof to thereby axially move shaft 29 to in turn adjust the anode member 21. Spring 41 tensions the piston assembly by contacting disc 31 to urge the adjusting mechanism inwardly towards the cathode with the overall control of the distance of travel maintained by the differential screw assembly.

To assist the adjuster in movement of the anode member it may be desirable to provide calibration means including another slot 42 in screw 38 normal to slot 40 with suitable markings or slits 43 in barrel 35. Such means are well known in the art and are not incorporated as a feature of the present invention.

What is claimed is:

1. An electron discharge device comprising a cylindrical envelope having two spaced parallel circular eonductors therein defining an interaction space, one of said conductors comprising a plurality of interdigital metallic fingers defining a delay line, electron gun structure positioned within the other conductor, output coupling means secured to the first member of said delay line, an adjustable metallic control element positioned in the region between said gun structure and said first delay line memher to thereby influence the trajectory of the electron beam prior to entrance into the interaction space, said control element comprising a solid metallic member having a fiat surface parallel to the electron beam and an inclined surface angularly disposed with respect to the axis of said output coupling means and differential screw adjusting mechanism secured to said control element to axially move said element along an axis normal to the electron beam.

2. An electron discharge device according to claim 1 wherein said control element has an overall height substantially equal to the height of said delay line interdigital metallic fingers.

Warnecke et a1 Mar. 26, 1957 Convert Mar. 4, 1958 

